Ecolab Inc. said Thursday that President Erik Fyrwald will leave the company to become CEO of Univar, a Redmond, Wash.-based distributor of commodity and specialty chemicals.

Fyrwald joined St. Paul-based Ecolab in December as part of its $8.3 billion acquisition of water management firm Nalco Holding Co. He had been Nalco's chairman and CEO.

In an interview, Ecolab CEO Douglas Baker Jr. said that Fyrwald's resignation was not unexpected.

"It's always different when you were a CEO and then you're not one," Baker said. "I knew it was likely he might move on if he found another opportunity."

Baker said Fyrwald had agreed to stay on while the two companies were combining their operations. His last day of work at Ecolab will be April 30, Baker said.

As Ecolab's president, Fyrwald had continued to oversee Nalco's energy and water management businesses, which account for about 40 percent of the post-merger revenue of more than $11 billion. Baker said there are no plans at this time to name another president and that he will now oversee those operations. Ecolab's other businesses make sanitation and pest elimination products.

In a statement, Fyrwald said: "It is difficult to leave this terrific company, as well as my many Nalco associates, but I look forward to this next phase of my career with excitement."

Univar last year generated $9.8 billion in sales, according to the privately held company's website. It says it is one of the world's largest independent chemical distributors, with a No. 1 market position in the U.S. and Canada.